In an upright vacuum cleaner, all of the parts of the vacuum cleaner, particularly the blower, dirt collection chamber, handle and the cleaning head are combined in one device that is held in the hand and guided by the user. This type of vacuum cleaner has the advantage that no bothersome hose is present during use, and the entire vacuum cleaner can easily be guided using one hand. Such vacuum cleaners are very popular, especially in the USA. However, the invention can also be applied without restrictions in other types of vacuum cleaner (canister cleaners).
When handling a floor vacuum cleaner, a pressure load is applied to the floor surface to be cleaned via the cleaning head. Particularly in upright vacuum cleaners, the entire weight of the vacuum cleaner always rests with all accessories on the cleaning head. This is cumbersome, particularly when especially soft floor coverings are to be cleaned. The cleaning head then sinks deeply into them, thus impeding the flow of aspirated air. The cleaning performance drops rapidly.
This phenomenon occurs particularly with a new generation of carpets. The manufacturers have transitioned to the use of finer filaments with a diameter that is reduced by about 25% and, as a consequence, the filament count has increased from about 150 to 350 filaments per yarn. This results in especially soft carpets. Noteworthy here are the “Caress” products by the Shaw Company and the product “Smart Strand” of the Mohawk Company. These carpets have such a soft nap that upright vacuum cleaners sink deeply into it. In doing so, the edges of the suction mouth bury themselves forcefully into the nap, thus strongly and unpleasantly increasing the force that is required to push the vacuum cleaner. Moreover, the brush roller in the suction hole of the cleaning head is strongly braked by contact with the fiber nap. The drive can be overloaded as a result, which constitutes a safety risk and leads to the triggering of protective devices.
Previously, any height adjustment that might be available on the cleaning head was used as a stopgap. Alternatively or in addition, a secondary air hole can be provided to reduce the negative pressure in the suction conduit leading from the suction hole. This can also lead particularly to the roller space housing the brush rollers. However, these measures lead to an extreme worsening of the suction characteristics.
Against this backdrop, in order to achieve optimum suction characteristics, what would actually need to be developed are novel vacuum cleaner nozzles. Particularly in upright vacuum cleaners, however, cleaning heads can be changed only with great difficulty, so that the entire device would have to be changed. What is more, it is difficult to design such a new vacuum cleaner nozzle so that it is equally suited to conventional carpet floors as well.